Abstract

Excitons in rubrene single crystals dissociate into free charge carriers via two mechanisms whose relative importance depends on the illumination wavelength through the optical penetration depth into the crystal. The first mechanism is defect-induced dissociation in less than 10 ns after photoexcitation. For low photoexcitation densities, about 10% of the excitons that survive radiative recombination dissociate through this channel. The second mechanism, affecting the remaining 90% of the excitons, involves a previously reported state localized close to the surface of the crystal that leads to a delayed release of photocarriers a fraction of a millisecond after photoexcitation.

Received 18 December 2009Accepted 12 April 2010Published online 05 May 2010

Acknowledgments:

This research at Lehigh has been supported by the donors of the American Chemical Society Petroleum Research Fund (Grant No. 45741-AC10). The work at Rutgers has been supported by NSF under Grant Nos. DMR-0843985 and ECS-0822036.

Abstract

Excitons in rubrene single crystals dissociate into free charge carriers via two mechanisms whose relative importance depends on the illumination wavelength through the optical penetration depth into the crystal. The first mechanism is defect-induced dissociation in less than 10 ns after photoexcitation. For low photoexcitation densities, about 10% of the excitons that survive radiative recombination dissociate through this channel. The second mechanism, affecting the remaining 90% of the excitons, involves a previously reported state localized close to the surface of the crystal that leads to a delayed release of photocarriers a fraction of a millisecond after photoexcitation.